Average runoff in the Nation's rivers and streams during water year 2016 (10.81 inches) was higher than the long-term (1930-2016) mean annual runoff of 9.31 inches for the contiguous United States (fig. 1). Nationwide, the 2016 streamflow ranked 12th highest out of the 87 years in 1930-2016. Note that in some previous water year summaries (before 2011) prepared by the USGS, the median runoff, not the average runoff, was compared among periods.

Figure 1. Annual runoff in the United States, 1930-2016

Streamflow levels were below normal in Connecticut, Rhode Island, Alaska, Massachusetts, Arizona, New Jersey, Montana, New York, Pennsylvania, and Puerto Rico-Virgin Islands (fig. 2). Streamflow was above normal in Michigan, Kansas, Kentucky, Oklahoma, South Carolina, Illinois, Nebraska, and Minnesota. Streamflow was much above normal in North Carolina, Missouri, Arkansas, Wisconsin, Louisiana, Iowa, and Texas. Most States had streamflow in the normal range.

Figure 2. Statewide streamflow ranks of the United States for 2016 relative to 1930-2016 mean annual streamflow.[**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

The United States (including Puerto Rico– Virgin Islands and the District of Columbia) is divided into 21 large drainages, or water-resources regions (fig. 3). These water-resources regions are based on surface topography and contain the drainage area of a major river, such as the Columbia River; the combined drainage areas of a series of rivers, such as the Texas-Gulf region, which includes several rivers draining into the Gulf of Mexico; or the area of an island or island group. Waterresources regions provide a coherent, watershed-based framework for depicting streamflow variations.

Figure 3. Water-resources regions of the United States.

Below normal streamflow levels were reported in the Alaska, Lower Colorado, and Caribbean regions (fig. 4). Above normal streamflows were reported in the South Atlantic Gulf and Lower Mississippi regions. Much above normal streamflow was reported in the Upper Mississippi, Arkansas-White-Red, and Texas-Gulf regions.

Figure 4. Regional streamflow ranks in the United States for 2016 relative to 1930-2016 mean annual streamflow.[**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

Autumn (October- December) streamflow levels were below normal in Connecticut, Rhode Island, Puerto Rico-Virgin Islands, and Nevada (fig. 5). Above normal streamflows were reported in Kansas, New Mexico, Hawaii, Mississippi, Kentucky, Minnesota, South Dakota, Virginia, Alabama, Louisiana, Georgia, Tennessee, and Washington. Much above normal streamflows were reported in Arkansas, Illinois, Wisconsin, Nebraska, Oklahoma, South Carolina, and Texas. Streamflows were reported at record high levels in Iowa, Missouri, and North Carolina. Nationwide, autumn-season streamflow ranked third highest out of 87 years.

Figure 5. Autumn (October-December 2015) statewide ranks in the United States relative to 1930-2016 mean annual streamflow. [**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

Winter (January-March) streamflows levels were much below normal in Hawaii (fig. 6). Above normal streamflows were reported in Idaho, North Carolina, South Carolina, Mississippi, Oklahoma, Arkansas, Washington, New Hampshire, and Vermont. Streamflow levels were much above normal in Texas, Louisiana, Michigan, Iowa, Minnesota, Maine, and Wisconsin. Nationwide, winter-season streamflow ranked 12th highest out of 87 years.

Figure 6. Winter (January-March 2016) statewide ranks in the United States relative to 1930-2016 mean annual streamflow. [**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

Spring (April-June) streamflows were much below normal in New York, Vermont, New Hampshire, Pennsylvania, Arizona, Massachusetts, and New Jersey (fig. 7). Below normal flows were reported in Connecticut, Maine, Oregon, Tennessee, Rhode Island, Washington, Montana, and North Dakota. Above normal streamflows were reported in Nebraska. Streamflows at much above normal levels were reported in Texas. Nationwide, spring-season streamflow ranked 62nd highest out of 87 years

Figure 7. Spring (April-June 2016) statewide ranks in the United States relative to 1930-2016 mean annual streamflow. [**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

Summer (July- September) streamflows were much below normal in Massachusetts, Rhode Island, Connecticut, New Hampshire, Arizona, Georgia, Alabama, Maine, and Washington (fig. 8). Below normal streamflows were reported in Montana, Wyoming, Vermont, Alaska, New York, Oregon, Idaho, and Pennsylvania. Above normal streamflows were observed in Texas, North Dakota, Indiana, and Arkansas. Much above normal streamflows were reported in Kansas, Missouri, Hawaii, Wisconsin, Kentucky, Illinois, Iowa, Louisiana, and Minnesota. Nationwide, summer-season streamflow ranked 32nd highest out of 87 years.

Figure 8. Summer (July-September) statewide ranks in the United States relative to 1930-2016 mean annual streamflow. [**For Puerto Rico-Virgin Islands, 73 years of available data were used and the rank was adjusted accordingly]

In any given month, it is expected that the average streamflow at 5 percent of the streamgages will be very high (greater than 95th percentile) and 5 percent will be very low (less than the 5th percentile). The percentages of streamgages reporting very high streamflow in November, December, January, February, and August of water year 2016 were higher than expected (7, 19, 7, 9, and 6 percent, respectively; fig. 9). In contrast, there was only one month (September) during which percentages of streamgages reporting very low flows were greater than expected (6 percent).

Figure 9. Percentage of streamgages with very high and very low monthly streamflow, October 1999-September 2016.